dives, techniques

Remote strobes

ERB_4588.jpgIt’s been a while since I played with remote strobes, so this weekend (having been been blown out by poor Bank Holiday weather) decided to try this technique in a local quarry. In a bid to get the creative juices working at a less familiar site, my buddy and I picked the National Dive Centre in Chepstow, a location I have dived less often than other fresh water sites in the Midlands.

The idea with remote strobes is to light a subject without using the strobes attached to the camera. This has the advantage of using a light source close to the subject but further away from the camera and so giving good lighting but with a minimum of backscatter.

The NDAC, like many quarries has a lot of scrap metal and I chose a Wessex helicopter as my subject. The aircraft was reasonably intact and has a large (dark) internal space. There’s a lot of setup time needed for remote strobe work and I was privileged to have a buddy prepared to set aside his camera and carry the extra strobes for me. It was just as well really, as of the two strobes I was hoping to place, one of them refused to work at all (despite having worked when I tested it before the dive). The vis was quite good (about 8-10m) and so I tried working from further back than usual, to catch the whole aircraft. I tucked the strobe (a Sea & Sea YS-110) inside the doorway, set on half power and pointing inward toward my buddy, who swam slowly out of the doorway.

The exposure was set as if for available light only, with the ISO high enough to provide a shutter speed fast enough to freeze the bubble motion (1/100s); since I was at least a few feet from the nearest part of the wreck, an aperture of f/8 was enough to ensure the whole frame was in focus. I used a single strobe on a low power setting solely to trigger the remote strobe.

I had my buddy shine a torch towards the strobe so that the flash light is “connected” to the subject. It takes a lot of practice to get all the aspects of this technique right and in hindsight, the strobe is not far enough behind the doorway, some flare is still visible. The diver is perhaps rather smallĀ in the frame and so the effect of the remote strobe is rather subtle; on the whole I think it needs a smaller subject, so that I can have the whole wreck but with the diver larger in the frame. Just another reason to go back and try again…

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equipment, techniques

Macro magnification

Having tried my lovely new Nikon 105mm macro lens out on a recent trip to Scotland, I had borrowed a Nikon diopter and also used a teleconverter. Now I had discovered that I was able to get some pleasing images, I was interested in making some measurements.

By using different combinations of these three items (lens, teleconverter and dioptre) different magnifications can be obtained, but as usual there are trade offs to be made. On one hand, a teleconverter increases magnification without needing to get closer (ie same working distance), but the optics absorb some light, which means either brighter illumination or a larger aperture, which in turn reduces the (already very narrow) depth of field. On the other, a dioptre lens increases magnification without absorbing so much light, but reduces the working distance.

So which is the best combination to choose? The first step, I felt was to try all the combinations and measure the magnification, working distance and depth of field. This would provide me with objective data to make decisions.

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It seems to boil down to working distance- the dioptre is likely to give better results if the subject is suitable- shorter working distance (so hopefully less backscatter) coupled with higher magnification. However, the teleconverter will help with more skittish subjects because it gives high magnification at a longer working distance, but relies on not having too much suspended matter in the water. Using both is a possibility, will require some care to ensure that the appropriate part of the image is in focus, due to the wafer thin depth of field.

equipment, techniques

DIY fibre snoot

During my recent trip to Scotland, I was happy enough with my composition and the sharpness of the super macro images I attempted. However, on closer examination of the images, I found the lighting was not to my liking. The trouble is that when lighting small subjects (a few millimetres in size), I want the subject lit without lighting up the background (or the suspended stuff in the water).

The job of a snoot is to restrict and direct the light from the strobe. I have tried before with plant pots and plumbing parts, but have not been happy with the results. Either the light is not snooted enough, or there is too much
light loss.

There are some very good commercially available products, but these are quite expensive, so I was keen to pursue the DIY route. During my googling of the subject, I came across Rob White’s excellent photo site, where he described how he made a fibre-snoot from inexpensive parts. He was quite willing to offer me extra advice, and I had to give it a go!

20140318-223208.jpgThe fibre snoot in place. I first used a neoprene sleeve to hold it there, but this was not secure enough when I tried it in the garden.

20140318-223221.jpgthe snoot base is made from the middle of a DVD “cake box”, the arm is a loc-line kit I got cheaply from eBay and inside is a length of 6mm dia “optical fibre”. I use quote marks because at that large diameter it is not so much an optical fibre as a light guide. I works, though. You can see the arm is off centre and aligned to one of the flash tubes, to maximise light output.

20140318-223230.jpgThe fibre is slightly recessed in the end of the arm and the orange fitting is covered in black insulating tape to cut light loss.

20140318-223242.jpgI decided to use the screw threads built into the strobe head. These two short M3 screws fit nicely, though the black plastic is more flexible than I would like though. I’ll still use the neoprene sleeve I think.

20140318-223250.jpgThis shot gives an idea of the working distance at the near point, when using a +5 diopter on the Nikkor 105mm macro lens. A short working distance, but workable, i feel. I found it fairly easy to set up (in air!) on a static subject. Going to be challenging underwater, to not crash the end of the snoot into the subject.

20140318-225437.jpgThis shot gives an idea of the size of the pool of light from the snoot. The tip has an aperture about the same as the light guide (6mm).

20140318-225448.jpgAn early shot at closest focus of the 105mm lens.

20140318-225454.jpgSame subject using +5 diopter. Happy enough with the lighting.

20140318-225501.jpgAn photo taken outside- heather flowers. This is using the fibresnoot (only just out of shot), the 105mm lens and +5 diopter. Nikon D200, ISO 400, 1/160, f/32. strobe output about 3/4. Nice black background and fairly pleasing lighting without being too obviously “snooted”.

20140318-225507.jpg Exactly the same subject and optics, but not using snoot. Although I like the background in this shot, underwater this would be more “messy” and with more backscatter. I don’t like the hotspot in the foreground, either- needed to point the strobe “out” more.

The next step is to try a narrower tip…..

dives, techniques

Wrecked lighting

The chance to dive two wrecks in clear warm water made me think of trying remote strobes again. During my Malta trip, we made a series of dives at Cirkewwa Point, which has two excellent wrecks- a military patrol boat, the P29, and a tug boat, Rozi. I had this technique in mind before the trip and had brought with me a spare arm, slave sensor and a small lead block. This allows me to position a strobe out of view of the camera, triggered via the slave sensor by the on-camera flash. The idea is to light up a subject which is difficult to light directly by on-camera strobes (eg further away from the camera) and minimising the backscatter which is usually caused by strong lighting. The technique requires some discipline as, in addition to carting extra gear on the dive, it takes time to set up. I always feel that time is limited enough on a dive, particularly at the 30m depth of the two wrecks at Cirkewwa, but I’d rather a single excellent shot from a dive than a card full of mediocre images. Here are two images, from two separate dives- the first is on the frigate wreck, P29 and the second is the bridge of the tug boat Rozi. You can be the judge of whether I succeeded.

Thanks must go to my patient model, Trevor Rees.

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techniques

Small is beautiful

Polycera quadrilineata
A small nudibranch (Polycera quadrilineata) on a kelp frond in Loch Long. Nikon D200 + 60mm Micro Nikkor lens and single Sea & Sea YS-110 strobe and "bottle snoot"

This small nudibranch (less than 1cm) was one of very many crawling on the stalks of kelp in less than 2m of water in Loch Long. I took this image on the second of two dives at the site. The first time I had gone in with a wide-angle lens, looking to take some close-focus images and/or diver images. However the topology and poor vis did not allow me to produce any images I was proud of; in fact I lost my buddy for a large part of the dive. As we emerged together, I was feeling a little disappointed, but he was raving. “What a fantastic site! Did you see all those nudibranchs? I found plenty to work on“, and so on. I couldn’t believe I hadn’t seen them. It just goes to show how much the eye tunes in to a certain type of subject. Because I was searching for things bigger than a coke can, I did not notice the exquisite but tiny creatures.

On my second dive, after a swift lens change and grabbing my bottle snoot, I saw so many of the little critters that I was amazed I hadn’t seen them last time. They were so plentiful that I was spoiled for choice and able to find several subjects in just the right location to help me shoot them from a good angle. I’ll have to remember that when some divers say a site is boring because there’s nothing to see…

techniques

Corkwing Wrasse

corkwing wrasseI took this image just off the breakwater at Plymouth. I spent about 30 minutes watching this male Corkwing Wrasse building a nest to impress its female. It made an excellent subject because it was behaving in a very predictable way, swimming in a loop between patches of seaweed and its nest. I shot this in the traditional way – with a black background. Soon after, returning to the site during a splash-in competition, I decided black backgrounds were boring and went for a behaviour shot to capture the male building its nest. It was a total flop and a quite uninteresting shot. I should have stuck to my original idea!

As a postscript, my good friend Rob Bailey returned to exactly the same site (and possibly the same fish) the following year and took a wonderful shot of the male building its nest. He ended up winning awards with it (see it here). Just goes to show it’s all in the execution….

techniques

Silhouette

inside the Scylla
Inside the Scylla

This image was taken inside the Scylla on Whitesand Bay in Plymouth, using a remote strobe on the diver to illuminate the area behind him. The vis was not to clever when I shot this, so I tried out a b+w conversion to try to accentuate the details of the wreck. I think I should have shot some at a higher ISO to get some more grain.